1. The construction unit shall conduct welding process evaluation on the steel, welding materials, welding methods, post weld heat treatment, etc. used for the first time, and determine the welding process based on the evaluation report. The welding process evaluation should be carried out in accordance with the current national welding regulations for building steel structures and the welding process evaluation for steel pressure vessels.
2. Welders must pass the examination and obtain a certificate of qualification before engaging in welding work. The certificate of conformity should indicate the welding conditions and validity period. Welders who have stopped welding for more than 6 months should be re evaluated.
3. When welding, welding rods with peeled off coating or rusted core, damp and clumped flux, and melted slag shells shall not be used.
4. Welding wires and nails should be cleaned of oil and rust before use.
5. Welding rods, fluxes, and studs should be baked according to the baking time and temperature specified in the product manual before use. The purity of the protective gas should meet the requirements of the welding process qualification. After baking, low hydrogen welding rods should be placed in insulation drums and taken out as needed.
6. Before welding, the welder should double check the quality of the welded joint and the treatment of the welding area. When it does not meet the requirements, it should be repaired and qualified before welding can be carried out.
7. Butt joints, T-joints, corner joints, cross joints, and other joint welds, as well as joint and corner joint combination welds, should be equipped with arc and exit plates at both ends of the weld, and their materials and groove forms should be the same as those of the welded part. The length of the arc ignition and led out weld seam in submerged arc welding should be greater than 50mm; Manual arc welding and gas shielded welding should be greater than 20mm. After welding, gas cutting should be used to cut off the arc and guide plate, and they should be ground flat without being knocked down by a hammer.
8. When welding, welders should follow the welding process and not freely weld or strike an arc on the base metal outside the weld bead.
9. The corner of the fillet weld should be continuously welded around the corner, and the distance between the starting and falling arc points and the end of the weld should be greater than 10.0mm. The end of the fillet weld should not be equipped with continuous welds with arc starting and exit plates. The distance between the starting and falling arc points and the end of the weld should be greater than 10.0mm, and the arc crater should be filled. 10. Carbon structural steel with a thickness greater than 50mm and low alloy structural steel with a thickness greater than 36mm should undergo preheating before welding and post heating after welding. The preheating temperature should be controlled between 100-150 ℃, and the post heating temperature should be determined by testing. The preheating zone is located on both sides of the weld, and the width=100% of each side should be greater than twice the thickness of the weld, and should not be less than 100mm. When the ambient temperature is below 0 ℃, the preheating and post heating temperatures should be determined according to the process test.
11. Multi layer welding should be carried out continuously. After each layer of welding is completed, it should be cleaned and inspected in a timely manner, and defects should be removed before welding.
12. A concave fillet weld should have a smooth transition between the weld metal and the base metal; Corner welds processed into concave shapes shall not leave cutting marks on their surface.
13. For butt and corner joint combination welds that require penetration, such as T-joints, cross joints, and corner joints, the weld leg size should not be less than t/4; The welding foot size of the connection weld between the web plate and the upper flange of the crane beam in the heavy-duty working system and intermediate working system with a lifting capacity greater than or equal to 50t is t/2 and should not exceed 10mm.
14. The welding of planks and beams adopts intermittent welding:welding 50, breaking 75. The welding height=100% is not less than 4. (1) The thickness of the weld seam is the thinner of the two welded components. (2) The length of the weld seam is the total length of the overlap between the two welded components. (3) Unless otherwise specified, all components are overlapped and fully welded, and the thickness of the weld seam is not less than the thickness of the thinner welded part of the two phases, and not less than 6mm. (4) Intermittent welding between platform patterned steel plate and platform beam.